CAN THE THERMAL THICKNESS OF THE CONTINENTAL LITHOSPHERE BE ESTIMATEDFROM MAGSAT DATA

The long-wavelength magnetic anomaly field derived from Magsat data is modelled by large-scale lateral magnetization variations in the conti nental lithosphere of Europe, central and southeast Asia. A simple mod el with six domains with uniform magnetization is shown to be consiste nt with this long-wavelength anomaly field. In this model, all major a lpine mountain belts are associated with magnetization lows and Proter ozoic cratons with magnetization highs. In particular, a significant c ontrast of magnetization is associated with the Tornquist-Tesseyre Lin e, the structural boundary between the Paleozoic western part of Europ e and the Proterozoic eastern domain. It is thus proposed that the mag netization contrasts and their associated long-wavelength magnetic ano malies may be attributed to differences of tectono-thermal age of the lithosphere. The main magnetization contrasts displayed by the model a re then shown to be associated with seismic velocity contrasts. This o bservation supports the hypothesis that magnetization variations are g enerated by magnetic sources distributed over the whole upper lithosph ere, down to the depth of the 600 degrees C isotherm. To support this conclusion, it is shown that the magnetic thickness predicted by the m agnetization model obtained is in good agreement with the depth of the 600 degrees C deduced from heat flow measurements. (C) 1998 Elsevier Science B.V. All rights reserved.